1. Field of the Invention
The present invention relates to a flexible grindstone that can be used to grind a curved surface of a workpiece such as stone speedily, as well as to a method of manufacturing such a grindstone.
2. Description of the Related Art
As a flexible coarse grinding tool having a large grain size (such as #40, #60, or #150) that is required to provide a large grinding force and to grind a large amount of material, there has been known a sheet-shaped flexible vitrified grinding tool having a plurality of grinding projections that include grinding grains. However, such a conventional grinding tool is poor in terms of making contact with a curved surface of a workpiece (such as stone), and involves difficulty in forming a smooth curved surface.
FIGS. 13 and 14 show a flexible vitrified diamond grinding tool invented by the inventors of the present invention (Japanese Utility Model Publication (kokoku) No. 4-5252). In FIG. 13, numeral 1 denotes cylindrical grinding chips, which are formed by disposing vitrified mixed powder containing grinding grains of diamond or cubic crystal boron nitride (CBN) in a die having a plurality of small holes arranged in line along concentric circles and then burning the powder.
Numeral 2 denotes a flexible base such as imitation leather impregnated with thermosetting resin. The grindstone portion is formed by the grinding chips 1 and the base 2.
To attach the grinding chips 1 to the base 2 in an integrated manner, the base 2 is impregnated with the thermosetting resin and then the grinding chips 1 are placed on the top thereof. Subsequently, the grinding chips 1 and the base 2 are heated, so that the thermosetting resin hardens while the grinding chips 1 and the base 2 combine into an integrated unit.
After the grinder portion is formed, a surface fastener 3 is attached to the back surface of the base 2 which has been hardened with flexibility. When grinding is performed, the surface fastener 3 is attached to a fastener of the attachment fixed to the output shaft of an electrically-driven or air-driven tool.